Effects of dietary protein levels on body pigmentation, growth and immunology of ornamental carp（Cyprinus carpio L.）

Abstract:

A feeding trial was conducted to investigate the effects of dietary protein levels on body pigmentation, growth and immunology of ornamental carp（Cyprinus carpio L.）(initial mean body weight: 5.85±0.19 g). The diet contained 130 mg/kg astaxanthins: Fish were fed with different protein levels （25.49%，30.84%，35.04%，40.68%，45.88%）and fed to apparent satiety to these groups of 20 fish for 60 days. The results showed that: The value of a* was highest in the protein level of 35.04%, no significant differences compared with protein level 40.68%(P<0.05), but obviously higher than other experimental groups (P> 0.05). The concentration of carotenoid in the skin of fish had significant differences from other experimental groups (P<0.05)at the same level while the highest value in the group protein level 45.88%.The highest body weight gain and feed conversion ratio occurred in the protein level 35.04%. There were no significant effects on LZM,CAT and LDH (P> 0.05).While the activity of SOD decreased obviously at the protein level of 45.88% (P<0.05). The results of this study also illustrated that the utilization of astaxanthin of ornamental carp（Cyprinus carpio L）did not improve constantly with the increase of protein level in diet.